When assessing a patient diagnosed with diabetes insipidus, what symptom does the nurse know is most indicative of this disorder?

Rationale: A. Fatigue is incorrect because, although patients with diabetes insipidus (DI) may experience fatigue, this symptom is nonspecific. Fatigue can result from many conditions, including dehydration, electrolyte imbalances, chronic illness, or sleep disturbances. In DI, fatigue may develop secondary to fluid and electrolyte loss, but it is not a primary or diagnostic feature of the disorder. B. Polydipsia is correct because it is the most indicative and classic symptom of DI. Diabetes insipidus results from either a deficiency of antidiuretic hormone (ADH, also called vasopressin) in central DI or the kidneys’ inability to respond to ADH in nephrogenic DI. Without adequate ADH activity, the kidneys cannot concentrate urine, leading to the excretion of large volumes of dilute urine (polyuria), sometimes up to 3–20 liters per day in severe cases. The body attempts to compensate for this fluid loss by triggering intense thirst (polydipsia), often resulting in the patient drinking large amounts of water to prevent dehydration. Polydipsia is thus a hallmark symptom and a key diagnostic clue for DI. C. Weight gain is incorrect because the fluid loss associated with DI typically causes weight loss rather than gain. Patients may have decreased body mass due to the ongoing loss of water and potential electrolyte depletion. Weight gain is not associated with DI unless there is excessive water intake beyond renal capacity, which is uncommon. D. Diarrhea is incorrect because DI affects renal water reabsorption, not gastrointestinal function. Diarrhea is unrelated to the pathophysiology of DI and may indicate a separate gastrointestinal issue rather than the endocrine disorder itself.